Delivery system for bifurcation stents

ABSTRACT

Systems for aligning and deploying side branch stents comprise a catheter having a side branch sensor at or near a distal end thereof. Methods comprises rotating and axially transitioning the catheter until the sensor is brought into alignment with an opening to the side branch vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/439,707 (Attorney Docket No. 32164-706.201, now U.S. Pat. No.______), filed May 23, 2006, which claims priority from U.S. ApplicationNo. 60/684,624 (Attorney Docket No. 32164-706.101), filed on May 24,2005, the full disclosures of each are incorporated herein by reference.

The disclosure of this application is also related to that of U.S.patent application Ser. No. 11/330,382 (Attorney Docket No.32164-704.201), filed on Jan. 10, 2006, the full disclosure of which isincorporated herein by reference.

BACKGROUND Field of the Invention

The present invention relates to medical methods and devices, morespecifically to medical devices intended to treat stenoses in thevascular system at or near bifurcated lesions.

Stenting is a common medical procedure mainly directed atrevascularzation of stenotic vessels where a blocked artery is dilatedand a stent is placed to maintain vessel patency following the dilation.The stent is a small tubular device, usually a metallic mesh or otherscaffold, that can be coated with drug or drug containing polymer.

While stents are successful in treating a variety of lesions in thevascular system, their success has been limited in the treatment ofbifurcation lesions in the coronary and carotid arteries. Often thestent mesh at bifurcation lesion is jailing the side branch access andlimiting blood flow to the side branch while interfering with the flowregimen.

Clinical literature describes the difficulties of using stents intreating bifurcated lesions. In addition to acute problems such as longprocedural time, complications can also result from limited side branchaccess during procedure and the need to use conventional stents outsidetheir design and labeling. The long term results are inferior and therate of restenosis is high compared to other lesions.

Attempts have been made to design a dedicated stents and deliverymethods for placing stents and bifurcated lesions in coronary andcarotid arteries. However, current solutions suffer from a variety ofshortcomings such as high profile relatively to conventional stents, theneed for a cumbersome delivery system to place the stent at the rightlocation and insufficiently accurate rotational positioning facing theside branch. Usually the side branch of the vessel is smaller than themain branch and the take off angle of the bifurcation varies. There isalso a need for ostial side branch support and local drug delivery tothe bifurcation area via stent coating.

Some of the prior art utilizes two guidewires to deliver and positionthe stent so that a side hole in the stent or a side portion area of thestent will face the side branch vessel. Examples can be seen in U.S.Pat. No. 5,749,825 Fischell et al., U.S. Pat. No. 5,755,735 Richter etal., U.S. Pat. No. 6,099,497 Adams et al., U.S. Pat. No. 6,596,020 Vardiet al., U.S. Pat. No. 6,706,062 Vardi et al., and U.S. Pat. No.6,048,361 Von Oepen.

The need for two guidewires and frequently for two lumens to accommodatethe guidewires requires a high profile system (i.e., a relatively largediameter) when compared to conventional stents and delivery systems andleads to difficulty in delivering the stent and longer clinicalprocedure. In many cases two guidewire bifurcation stent deliverysystems require also larger guiding catheters than conventional stentsdelivery systems. In addition, the physician has a very limited abilityto rotate the catheter to achieve rotational positioning, and the systemmust be guided to the location and radial position solely by thepre-placed guidewires. Due to the natural flexibility of the guidewiresand the large difference between the guidewire diameter (usually 0.35mm) and the side branch diameter (usually 2 mm or more), the positioningof the stent may not be accurate. The side portion of the stent may notbe facing the central part of the side branch, and in many cases only aportion of the side hole or the side portion of the stent will face theside branch of the vessel. Attempts to improve alignment by usingstiffer guidewires may result in other problems. For example, theconventional metallic guidewires affect the local geometry in thebifurcation site and mask the real bifurcation angle. Once theguidewires are pulled out at the end of the procedure, the side branchangle restores its original position sometimes leaving a gap between thestent and the arterial wall leading to inferior clinical outcome.

Other systems designed to deploy stents that provide at least partialsupport to the side branch opening utilize two balloons. Examples may befound in U.S. Pat. No. 4,994,071 (assigned to Cordis) in applications US2005/0102019 and US 2005/0060027 assigned to Advanced StentTechnologies. Those systems suffer from complexity and the need toinflate two separate balloons, a high profile, and poor deliverabilityresulting from an excessive stack of material below the stent that addto the stiffness of the working end of the system.

When treating a bifurcation lesion using the above systems, thephysician places one guidewire in the main vessel and a second guidewirein the side branch. This is done to maintain access to both vessels. Acommon problem associated with such use of two guidewires is that theguidewires tend to wrap around each other. This phenomenon is known as“wire crossing” and is very common when catheters needing two wirescatheters are being used. Current bifurcated stent delivery catheterswhich utilize two guidewires and can not be delivered through suchcrossed wires. In some cases, the physician needs to retrieve the wholesystem including the guidewires, thus increasing the chances ofmorbidity and procedural complications. The physician has to rewire thearteries and start over with a new system.

For these reasons, the currently available delivery systems forbifurcation lesions are limited in performance and in the ability toaccurately position the stent axially and ensure that the side portionor side hole of the stent are facing the side branch of the vessel. Itwould be desirable to provide catheter systems for delivering stents forbifurcation which need only a single guidewire for placement.

BRIEF SUMMARY OF THE INVENTION

This invention discloses a delivery system for bifurcated stents havingside branch portion. The system comprises having a catheter singleguidewire lumen with an expandable or other stent deployment shell orother stent deployment region near the distal end of the catheter usedto deliver and deploy the stent with at least partial deployment of theside branch portion.

In one embodiment the catheter shaft is designed to rotate in responseto torque applied by the operator.

In one embodiment the system includes a sensing mechanism to identify aside branch opening. Exemplary sensing mechanisms include an imagingcomponent and a penetrating element which deploys laterally into theside branch when the stent is properly oriented toward the side branch.

In one embodiment the system is aligned by signals from the operatorusually via electronic circuits. The distal part of the catheter isdesigned to rotate in response to the electronic signals. Markers canalso be used to help accurately position the stent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general depiction of the catheter of the present inventionwith an undeployed bifurcation stent carried on a deployment balloon.

FIG. 2 is a general depiction of the stent of FIG. 1 after deployment.

FIG. 3 shows a distal end of the catheter with a sensing mechanism toidentify side branch location.

FIG. 4 shows an indicator located on a proximal hub of the catheter ofFIG. 2 to provide the physician with an indication when the system isoriented properly.

FIG. 5 shows the size of the system relative to a 3 mm reference vessel.

FIG. 6 shows the size of a two wire system relative to a 3 mm referencevessel.

FIG. 7 shows a delivery system with “pop-up” marker to help identifyside branch location.

FIGS. 8A and 8B show a delivery system with a sliding marker to helpidentify side branch location.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a delivery system for bifurcated stentsor other prostheses having a main body and a side branch portion or aside hole. The phrase “side branch portion” includes any opening orstructure in the main body which is to be aligned with an ostium of aside branch lumen or vessel when the main body is in the main lumen orvessel. The side branch portion may be a simple hole in the form of acell or a slit in the prosthesis structure which is preselected to bealigned with a side branch vessel but which is otherwise similar toother cells, slits, or the like in the prosthesis. More usually,however, the side branch portion will be an enlarged or enlargeable cellwhich is distinguishable from the adjacent or remaining structure of theprosthesis. In other embodiments, the “side branch structure” comprisesa self-opening or balloon openable peripheral structure which isintended to bridge the circumference of the side branch ostium after theprosthesis is opened in the main branch. The bifurcated stents of thispatent are suitable for placement at all types of bifurcated lesions andlesions near bifurcations in the vessels or ostial lesions of all typesincluding aorto-ostial and anastomotic sites in which the side portionis located in one end of the prosthesis and will usually include flaredportion.

The stents or other prostheses to be delivered in accordance with thepresent invention usually have a generally tubular structure comprisinga main body that is capable of expansion by balloon inflation to supportthe main vessel and a side portion structure designed to expand at leastpartially into the side branch vessel and support the side branchostium. Additional balloon(s) may be used to complete the deployment ofthe side branch portion or the main body of the stent if needed.Examples of suitable side branch stents and prostheses are provided incopending application Ser. No. 11/330,382 (022246-000240US), thedisclosure of which has previously been incorporated herein byreference.

An example of such a stent placed on a delivery catheter is shown inFIGS. 1 and 2. FIG. 1 shows a balloon catheter 10 having at least onelumen for receiving a guidewire 70 and a separate balloon inflation. Abifurcated stent 30 is crimped over balloon 20 with an unopened sidebranch portion 40 (FIG. 1). The side portion 40 will usually be formedintegrally with the stent main body, but in other cases may be added tothe stent main body using laser welding or any other attachment process.Catheter shaft 12 has sufficient torsional stiffness to rotate (arrow14, FIG. 2) in response to torque applied at its proximal end 16 (FIG.4) by the operator. This torque response can be achieved for example byusing a braided shaft, stiffened shaft, hypotube or by using a suitablecore wire or by other conventional methods used in the industry toimprove the torque response of at least part of the shaft. The balloon20 will usually be a conventional balloon (nylon blend, pebax blend, orthe like) of a type used for the deployment of the stents and vascularprostheses. The side branch portion 40 is initially closed. To improvetorque response and avoid uncontrolled motions (“whipping”) of thedistal end which could result from torque build-up in the shaft, dampersections (not illustrated) may be added to the shaft structure in a formof a non-braided section with mechanical properties different than thebraided section.

FIG. 2 shows the stent 30 after expansion by the balloon 20 with theside branch portion open 40. The catheter shaft 12 has a singleguidewire lumen 14 terminating at distal port 32. Conventional balloonmarkers 60 may be used to help the operator identify the location of thesystem in the vessel, and a sensing mechanism 50 such as an ultrasonictransducer, a laser diode, a semiconductor diode or other sensor, can beused to help orient the system and determine the location of the sidebranch.

In one embodiment the sensing mechanism 50 comprises an imagingcomponent including at least one fiber optic (or other common laserlight transmission element) located at or near the side branch portion40, typically on the circumference of the distal end of the cathetershaft 12, preferably near or on the balloon 20 in the case of selfexpandable stents or other prostheses. Light or other detectableradiation can be transmitted through the fiber optic system andreflections can be detected by the fiber optic system to help locate thebranch. Laser radiation reflected back from different parts of thevessel wall can be monitored to identify changes in the vessel structureto in turn locate a side branch opening. In particular, the system canbe used to detect reflections or calculate energy loss due to absorptionin different areas of the luminal wall. One fiber can be used as bothtransmitter and detector or alternatively different fiber(s) can be usedeither as a bundle or distributed on the circumference of the distalarea of the catheter.

In another embodiment, the sensing mechanism may be located on aguidewire 70 used to deliver the system. Alternatively the sensingmechanism can be located on another elongated member exchanged with theguidewire in the central guidewire lumen 14 of the shaft 12. In allcases the sensor can be moved within the distal end of the catheter tohelp identify the side branch and may be moved backwards and optionallywithdrawn anytime after indicating the location of the side branch.

Once the axial location of the catheter is determined using the markers60, the sensing mechanism can be moved towards the distal end of thecatheter. The operator can then rotate the catheter using feedback orother indications received from the sensing mechanism to helprotationally align the side hole in the stent with the side branch osprior to deployment of the stent.

FIG. 3 illustrates a protocol which identifies the side branch using asensing mechanism 80 located on the shaft of the catheter below thestent 30 and the balloon 20. The operator rotates the catheter shaft 12and receives feedback from the sensing mechanism 80. As illustrated inFIG. 3, the sensing mechanism 80 comprises a sensor such as an imagingsensor having a field of view 82 passing through the side branch 40 tohelp indicate the location of the side branch ostium O. In otherembodiments, the sensor could be an electro-chemical sensor capable ofdetecting proximity of the side branch. If the sensor is located nearthe balloon, it can detect the presence or absence of tissues. Thesensing mechanism can be located at or near the distal end of thecatheter 10 either within the balloon 20 or outside of the balloon.

In another embodiment, a working end of the catheter is mounted on aseparate rotatable shaft with a small mechanical drive, such as aminiature electrical motor, servo mechanism, or other remotely operateddrive mechanism. The operator can orient the working end of the catheterby remotely rotating the separate shaft of the catheter to achieve acorrect position using any of the sensory feedback mechanisms discussedherein. Alternatively the operator can control the motion of the distalpart fully or partly by using a joystick or other manual interfacedevice that can send signal to the distal area of the catheter.

In yet another embodiment, the sensing mechanism is linked to anautomatic orienting system circuit. In this embodiment the system has acontroller (typically using a digital processor) to monitor therotational position signal sent from the sensing mechanism. This signalis used to determine if the working end is accurately oriented. If it isnot correctly positioned, the automatic orienting system will rotate theworking end until correct orientation is achieved. In this embodiment,the system is self-aligned using a feedback loop between the sensingmechanism and the controllable electrical motor or other positioner toproperly orient the stent. It is possible for the operator to deliveranother wire or device to stabilize the location and orientation of thedistal end. For example, the operator can deliver guidewire or fiberoptics to the side branch to help stabilize the system or in some caseanchor the system.

FIG. 4 shows a proximal catheter hub 16 having an operator interfacewith a red light 84 and a green light 86 (or equivalent visual oraudible signals) to notify the operator if the stent achieved thedeployment position (green light) or should not deploy (red light). Inthis example, the power source for the sensor may be integrated with thecatheter and the complete system can be a singe use system.

In one embodiment the operator interface and associated circuitry isseparated from the catheter and can be used multiple times. Theinterface can be linked to the sensor or to a side branch locator bywireless connection or by physical connector. The power source can beintegrated (battery for example) or external power source.

FIG. 5 shows the profile of the system in respect to a 3 mm vessel nearbifurcation area. FIG. 6 shows typical profile of a two wire systemrelatively to the same vessel. The benefit of the single wire system isillustrated in those figures. By eliminating the need for a second wire86 as shown in FIG. 6 (and in come cases for a second balloon), thesingle wire system profile of the present invention may be 20% lowerthan a two wire system, usually 30% lower, and typically 50% lower. Forexample, the width of the stent over the balloon with the single wire(FIG. 5), will usually be no greater than 1.5 mm, preferably no greaterthan 1.4 mm, and often 1.2 mm or less over a portion distal to the exitpoint of any penetrating member through the side branch portion. In apreferred embodiment, the profile of the system is about 1 mm whendesigned for coronary vessels. For neuro vascular application the systemmay be much smaller, but for carotid application the system profilemight be larger.

For coronary bifurcations, the device is usually used in vesselstypically ranging from 2.5 mm to 5 mm in diameter (without stenosis).The single wire bifurcation system including the crimped coronarybifurcation stent of the present invention may be smaller than 1.5 mmand sometimes smaller than 1.4 mm, and typically close to 1.3 mm. Insome cases the profile of the bifurcation stent and delivery system canbe close to 1.2 mm and sometimes lower depending on the size of thestent and the specific anatomical location required. For purpose ofcomparison the profile of conventional non-bifurcation stents ondelivery systems is usually 1.2 mm typically close to 1 mm and sometimes0.9 mm or lower.

As a further comparison, a commonly used coronary guidewires has adiameter of approximately 0.35 mm. Typical guidewire lumen has ID (innerdiameter) of 0.43 mm and OD (outer diameter) of 0.58 mm. While addingthe size of the folded balloon and the wall thickness of the crimpedstent (usually approximately 0.41 mm), the stack of materials alone fora dual guidewire device with dual guidewire lumens is larger than 1.4mm. The actual profile of two wire system is typically larger than 1.5mm usually larger than 1.6 mm and frequently as large as 1.8 mm or more.In case that a second balloon is required to inflate the side portionthan the system will be in the high range of the above and sometimeseven larger.

FIG. 7 shows a single guidewire bifurcation stent delivery system 100that utilizes a single balloon 102 to deploy a bifurcated stent 104having a side branch portion 105. The positioning and orientation of thedelivery system is obtained using a protruding, resilient (“pop-up”)marker 106 that can be preloaded and released near the side branchbifurcation site SB. The marker is visible under fluoroscopic imaging.While the pop-up marker 106 is facing a vessel wall, it remainsconstrained. As the catheter shaft 108 is rotated (arrow 109), thepop-up marker aligns with the opening (os) of the side branch SB andenters the side branch. The appearance of the marker 106 in the sidebranch SB under fluoroscopic imaging indicates to the operator that theorientation is close to optimal and the stent 104 can be deployed.

In one embodiment the protruding marker has a soft tip to minimizevessel trauma. The protruding marker can be made of super elastic orshape memory alloys, such as nickel titanium, or elastic metals, such asstainless steel alloys, cobalt chromium alloys, MP35 or alike and othermetals. The protruding markers can alternatively be made of a polymersuch as nylon or nylon blend, pebax, or any other resilient,biocompatible polymer. Radiopaque material can be attached to the markerin order to make it visible to the operator. The radiopaque material canbe crimped, swaged extruded or co-extruded, bonded or placed on thepop-up marker system in any other conventional way known to theindustry. If NiTi is used while in it's shape memory state, theprotruding marker can be activated by changing the temperature of theNiTi structure thereby activating a memorized shape that was applied tothe marker system during processing.

FIGS. 8A and 8B show a single wire and single balloon delivery systemfor bifurcation stent 200 with a side branch portion 202. In thisembodiment, a moveable marker 204 can be slid in and out through a lumen206, partial lumen, slit or one or more hooks or short lumens on theshaft 208 of the catheter. The moveable marker assembly 204 comprises anelongated member, preferably made of metallic wire or ribbon or extrudedpolymer such as nylon or any other material with the required physicalproperties that will allow pulling and/or pushing the marker assembly inits passageway. The distal end 210 of the elongated member can be madeof marker material such as platinum Iridium or tungsten, or MRI visiblematerials, or other known marker materials currently used in theindustry. Alternatively the marker material can be attached or placed orbonded or linked to the end of the marker assembly. The marker assemblycan be pre shaped with a bend in such a way that when pushed out of itslumen 206 at or near the distal end of the catheter it will tend toprotrude and if pushed while in proximity to a side branch SB it willappear in the side branch and can visually identified by imaging systemsused in the procedure such as Ultrasound, MRI or CT. The distal end ofthe marker assembly 204 is designed to minimize vessel trauma whenpushed against the vessel wall. Such a design may include soft tip,polymeric extension, local loop or other options. The rotatable shaft208 consists of braided shaft section 211 with guidewire lumen 212moveable marker lumen 206 and inflation lumen 214. The diameter of thelumen can be small and need to comply with the marker assemblydimensions. If nickel titanium or steel ribbon is used for the assemblythe thickness of the material is usually 0.025 mm to 0.25 mm andsometimes in the range of 0.25 mm to 2.54 mm. The lumen can be designedto allow an interference fit for the marker, or it can be larger.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting the scope of the invention which is defined by the appendedclaims.

What is claimed is:
 1. A stent delivery system comprising: a cathetershaft having a stent deployment region near a distal end thereof; astent having a side portion on the stent deployment region of the shaft;and a side branch sensor on the catheter shaft, wherein the sensorcomprises an imaging component positioned on the shaft to view radiallyoutwardly through the side branch portion of the stent.
 2. A stentdelivery system as in claim 1, wherein the stent deployment regioncomprises a balloon which carries the stent.
 3. A stent delivery systemas in claim 1, wherein the catheter shaft has only one guidewire lumenextending through the balloon which carries the stent.
 4. A stentdelivery system as in claim 1, wherein the width of the stent on theballoon does not exceed 1.5 mm.
 5. A method for deploying a prosthesishaving a side branch portion in a side branch vessel in a main lumen,said method comprising: providing a catheter carrying the prosthesishaving the side portion; advancing the catheter in the main lumen untilthe side portion is proximate the side branch; imaging a wall of themain branch vessel with an imaging component carried on a shaft of thecatheter, which imaging component provides a view through the sideportion of the stent; rotating and/or axially positioning the catheterwhile observing the relative position of the side portion and the sidebranch vessel using said imaging component; deploying the prosthesisafter observing the alignment of the side branch portion and the sidebranch vessel.
 6. A method as in claim 5, wherein imaging componentcomprises an ultrasonic imaging transducer.
 7. A method as in claim 6,wherein the ultrasonic imaging transducer is aligned with the sideportion of the prosthesis.